New research on degrading microorganisms could help transform forensic medicine

Researchers have identified for the first time what appears to be a network of about 20 microorganisms that universally promotes the breakdown of animal meat. This discovery has significant implications for the future of forensic science, including the potential to provide crime scene investigators with a more accurate way to determine a body’s time of death.

“It’s really amazing that there are microorganisms that always show up to break down animal remains,” said Jessica Metcalf, an associate professor at Colorado State University. natural microbiology. “Hopefully, we can open up a whole new field of ecological research.”

The decomposition of dead biological material is one of Earth’s most fundamental processes. Organic plant wastes make up the majority of the materials that are decomposed, and this process is relatively well understood. However, little is known about the ecology of decomposition in vertebrates, including humans, and a deeper understanding of how humans decompose has the potential to advance forensic science.

This new study is a multi-year effort, involving the dissection of 36 cadavers at three different forensic anthropology facilities: University of Tennessee, Knoxville; was held. Sam Houston State University; and Colorado Mesa University. The bodies decomposed in various climates and seasons. The researchers then collected skin and soil samples from each decomposing body during the first 21 days.

Metcalf and her colleagues generated large amounts of molecular and genomic information from the samples. They then used that information to build a complete picture of the “microbial community”, or microbiome, present at each location. “Essentially, what microbes are there, how did they get there, how do they change over time, and what are they doing?” Metcalfe said. Ta.

Surprisingly, regardless of climate or soil type, the researchers found the same set of about 20 specialized decomposing microbes in all 36 bodies, she said. Moreover, these microbes arrived like clockwork at specific points during her 21-day observation period, and insects played a key role in their arrival.

“Regardless of how many outdoor variables are considered, we find that similar microorganisms arrive at similar times during decomposition,” Metcalf said.

The future of forensic medicine

Identifying the consistent composition and timing of the degrading microbiome has important implications for forensic science.

Metcalf and his collaborators, David Carter, a professor of forensic medicine at Chaminade University in Honolulu, and Rob Knight, director of the University of Honolulu’s Microbiome Innovation Center, used machine learning techniques and data from the new study, as well as previous studies. SAN DIEGO, Calif. – We’ve built a tool that can accurately predict the amount of time a body has passed since death, also known as the post-mortem interval.

“When you’re talking about death scene investigations, there’s very little physical evidence that you can guarantee will be present at every scene,” Carter said. “You never know if you’re going to find a fingerprint, leave a blood stain, or leave a camera footage. But there are always microorganisms.”

Additionally, these microbes may be particularly useful under the types of conditions investigated in the new study, Carter said. “We’re talking about an outdoor death scene,” he said. “Information can be difficult to gather in this type of investigation.”

Nancy La Vigne, director of the National Institute of Justice, finds this research particularly promising. “One of the important questions in any death investigation is, ‘When did this person die?'” La Vigne said. “This ongoing research shows promising results that can help predict time of death, identify deceased persons, identify potential suspects, and confirm or refute alibi.”

In addition to identifying the universal decomposers, the research team also sought to determine where this microbial community came from. Remarkably, the microbe could not be found in soil microbiome databases or human skin or gut microbiome catalogs, Metcalf said. But they discovered a universal decomposer in insects. “Insects appear to be introducing microbes,” Metcalfe said.

Other research uses

These latest findings are based on more than a decade of research by Metcalfe, Carter, and Knight. This includes an initial study in which mice were decomposed in different soils in a controlled laboratory environment, as well as a follow-up study in which four cadavers were decomposed at the Sam Houston Museum. National facility. Zach Burcham, a former CSU postdoctoral student in Metcalfe’s lab, helped lead the latest research.

“This research was a large-scale collaboration by a diverse team of knowledgeable scientists, and a brilliant example of what can be achieved when interdisciplinary teams work together towards a common goal.” This is an example,” Burcham said. “This dataset is truly unique and has implications ranging from microbial ecology to forensic science.”

In addition to forensic applications, Metcalf also sees other opportunities to leverage this new information. “We think there are a lot of potential applications across agriculture and the food industry,” said Metcalf, of CSU’s Department of Animal Science.

Metcalf also intends to expand his research in this area, including the possibility of examining differences in the microbial ecology of small and large vertebrates. “I feel like there are a lot of avenues open to us in terms of basic ecology and nutrient cycling,” Metcalf said.